Human T-Lymphotropic Virus type II (HTLV-II) is a human retrovirus related to, but distinct from other retroviruses that are identified causative agents of disease. Little is known about HTLV-II prevalence in the population or its disease associations because the study of HTLV-II has lagged, in part due to the lack of readily available reasonable cost assay reagents. We propose to construct recombinant clones of the HTLV-II proteins in an expression vector by Polymerase Chain reaction (PCR) amplification and assess the utility of the recombinant product as serologic reagents for large scale production and purification. Phase I objectives include construction of two clones of the HTLV-II envelope (env) gene in an E. coli expression vector and preliminary characterization of the expressed viral products. In Phase II, env will be cloned into additional expression systems (Saccharomyces and Neurospora), and the merits of the different vectors with regard to viral protein production, antigenicity and solubility compared. Other Phase II objectives include cloning of the balance of the HTLV-II antigens and preliminary purification strategy. Recombinant viral proteins produced in quantity having good solubility and serologic reactivity characteristics are good candidates for research and blood screening assay reagents.